High-frequency electron tube structure



March 1951 w. w. HANSEN ETAL 2,544,679

HIGH-FREQUENCY ELECTRON TUBE STRUCTURE Original Filed Oct. 25, 1941 INVENTORS W/LL/AM W HFINSEN fi/N E. WoooYq/QD Patented Mar. 13, 1951 HIGH-FREQUENCY ELECTRON TUBE STRUCTURE William W. Hansen and John vR. Woodyard, Garden City, N. Y., assignors to The Sperry Corporation, Great Neck Delaware N. Y., a corporation of Original application October 23, 1941, Serial No. 416,170, now Patent'No. 2,425,738, dated August 19, 1947. Divided and this apphcationv June 20, 1945, Serial No. 600,440

6 Claims, (01. 315-6) The present invention is directed to the .art including electron discharge devices operating at super-high or microwave frequencies of the order of 300 megacycles per second or higher, corresponding to wavelengths-of-the order of one meter or shorter. The present invention is more particularly concerned with such devices for multiplying a lower frequency to a value in this superhigh frequency range or for multiplying one microwave frequency to form a much higher microwave frequency. The present application is a true division of copending application'Serial No. 416,170 for High Frequency Electron Tube Structure, filed October 23, 1941, now Patent No. 2,425,738 granted-August 19. 1947.

In U. 8. Patent No. 2,281,935 granted May 5, 1942, to William W. Hansen (one of the present applicants herein) and Russell H. Varian, there is disclosed one form of apparatus suitable for generating oscillations of a super-high frequency and also for multiplying this frequency to a still higher harmonic frequency. Such devices operate upon the velocity modulation principle in which the velocities of the electrons of an electron stream are periodically varied at a predetermined frequency. Thereafter the velocityvaried electrons are passed through a field-free drift space in which the faster electrons overtake the slower electrons to form eectron groups or bunches, from which, in the case of a frequency multiplier, energy of a frequency harmonically related to the frequency of the velocity variation may be extracted.

Because of practical considerations, such frequency multiplier devices have low beam con-- version efliciency and high frequency gain; that is, the output high frequency power forms but a sma l fraction of the power used to produce the electron stream, and also only a smallfraction. of the high fre uency power supplied to produce the velocity modulation. Ordinarily, therefore, such devices require further amplification of the multi, plied frequency wave, suchlasshown in'this Patent No. 2,281.935. Amplifiers for this purpose are-generally .also of the velocity modulation type utilizing cavity resonators of the same type as are used in the frequency multiplier device, Such a system of a frequency multiplier feeding a separate amplifier is awkward and, cumbersome in operation, since Clifiioulties are experienced in accurately tuning all the many resonators to the proper frequencies and in maintaining these resonators tuned to thevproper frequency. Also, such systems are relatively inefi'icient, since two separate electron streams must be produced, each requiring independent power excitation, and since the increased number of resonators produce increased losses. Systems of the type shown in this patent are also difiicult to maintain stabilized in frequency, since changes in operating conditions, such as changes in exciting potentials or in ambient temperatures, cause marked changes in the frequency of the oscillations generated.

The present invention is directed toward improved frequency multiplying apparatus having greatly increased eificiency and more convenient time of operation as compared to such prior art as exemplified by this Hansen and Varian patent. According to one feature of the present invention. the oscillations whose frequency it is desired to multiply are produced independently of the multiplier device. This permits such oscillations to be produced from or controlled by frequency-stabilized sources, such as crystal-controlled oscillators, which may cooperate with frequency multiplier devices of conventional type to produce the wave whose frequency is to be multiplied by the apparatus forming the present invention. This may be termed a driven multiplier, as distinguished from an oscillator-multiplier shown in the Hansen and Varian patent.

According to another feature of the present invention, such a driven frequency multiplier is combined in the same device with an amplifier stage, using the same electron stream which serves to perform the frequency-multiplying function, and with a decreased number of tuned cir cults requiring tuning alignment or tracking.

According to the present invention, an electron stream is varied in velocity (velocity-modulated) at the fundamental frequency to be multiplied, preferably in response to the output of an independent source of oscillations of this fundamental frequency. These velocity-varied electrons are permitted to become bunched or grouped in the usual velocity-grouping fashion and serve to excite a resonant circuit, preferably of the cavity resonator type, which is tuned substantially to the desired harmonic of the fundamental frequency. Instead of utilizing this resonant circuit to supply the output harmonic frequency energy, it is preferred to leave this resonator floating, that is, unconnected to any load or source other than the electron stream itself. Such a tuned circuit or cavity resonator reacts upon the electron stream to produce further velocity variation of the electrons thereof and to enhance the amount of bunching at the desired harmonic frequency. As a feature of the present invention, the electron stream having this enhanced grouping or bunching is thereafter used to excite an output resonant circuit, also preferably of the cavity-resonator type, to which may be coupled any suitable load to be energized at this harmonic frequency. In this way the functions of frequency-multiplying and amplification are com-- bined in the same device, using only one electron stream and requiring only two resonant circuits tuned to the harmonic frequency.

Accordingly, it is an object of the present invenfundamental frequency resonator and an output harmonic frequency resonator. v

Further objects and advantages will become apparent from the specification, taken in connection with the accompanying drawing, wherein: Fig. 1 shows an elevational view of one embodiment of the present invention, partly in longitudinal cross-section.

In the drawing there is shown a cathode I8I of any suitable conventional type. Adjacent the cathode I8I is the entrance grid I82 of the input or buncher resonator I83. A suitable source of unidirectional potential (not shown) is connected between cathode I8I and grid I82 so that the electrons from cathode I8I are projected in the form of a stream through grid I82.

I84, a slightly dished rigid end wall I85 carrying grid I82, and a flexible wall I18 illustrated as in the form of an annularly crimped diaphragm, at the center of which is secured a tubular member or drift tube I85 providing the drift space and projecting axially within the cylindrical wall I84 in reentrant fashion. Drift tube I85 carries a second grid I11 closely adjacent to grid I82 and in alignment with the electron stream path. A flange I16 is also secured to drift tube I85 substantially parallel to the dished wall I86 of the resonator. Flange I19 cooperates with wall I88 to provide an effective lumped capacitance, permitting reduction in the physical size of the resonator I83 for the particular chosen fundamental frequency to which it is substantially resonant. Suitable coaxial line coupling arrangements 283 are provided, serving as terminals for supplying fundamental frequency energy to resonator I83.

As is well known, resonator I83 may have its resonant frequency adjusted by adjustment of the gap between grid I11 and flange I18 on the one hand and grid I82 and wall I88 on the other hand. In the present device such adjustment may be effected by adjusting the separation between a flange I89 rigidly connected to cylindrical resonator wall I84 and a second flange I93 rigidly connected to the drift tube I85, such adjustment being effected by adjustment of a plurality of symmetrically disposed tuning screws I88 threaded in flange I89 and abutting or recessed in flange I93.

A second similar resonator I81 is provided at the other end of drift tube I85. This resonator 4 I81 comprises a pair of grids I98 and I92 similar to grids I82, I11 and disposed in the path of the electron stream, grid I98 being mounted in the opposite end of drift tube I85 and grid I92 being mounted in a rigid end wall 288 of resonator I81. The resonator I81 is completed by a rigid cylindrical side wall 282 connected to wall 288 and a flexible end wall 289 connected to drift tube I85, and its resonant frequency may be adjusted by adjusting the separation between flange I93 and a further flange I91 rigidly connected to the cylindrical wall 282, as by means of a similar plura ity of tuning adjustment screws I88 threaded in flange I91 and bearing on flange I93. In this way resonator I81 may be tuned to the desired harmonic of the fundamental frequency energy supplied to resonator I83.

Resonator I81 may also be supplied with coaxial line terminals 288, mainly for use in accurately tuning resonator I81. These terminals 283'are preferably not used during operation of the device, although, when desired, small amounts of harmonic frequency energy may be usefully sup-" plied thereby to a desired load. 1

Connected to wall 288 and grid I92 is a further drift tube I85 at whose opposite end is mounted a resonator I95 similar in construction to resonator I81, and having a pair of grids in the electron stream path, similar to grids I98, I92. Ihis Resonator I83 is formed by a rigid cylindrical outer wall resonator I95 may also be tuned by means of'the tuning adjustment screws I88" which serve, through the flanges I99 and I98, to adjust the separation of the grids of resonator I95 in a fashion similar to that of resonator I81. Resonator I95 is tuned to the same harmonic frequency as resonator I81 and is provided with a pair of coaxial line output terminals I91 for supplying the harmonic frequency energy extracted from the electron stream by resonator I95 to the desired load. The electron stream, after passing through the grids of resonator I95, passes through a further tubular member I85 to a collector indicated at 28I to which the electrons give up their remaining energy.

In operation, the fundamental frequency energy derived from any desirable source, such as a crystal-controlled oscillator and conventional frequency-multiplier chain, is coupled to resonator I83 by one of its terminals 203, resonator I83 being tuned substantially to this fundamental frequency. In this manner a standing electromagnetic fleld is produced within resonator I83 having a strong alternating electric field component of the fundamental frequency extending axially of the stream between the grids I82 and I11. This alternating e ectric field component alternately accelerates and decelerates the electrons of the stream and thus velocity-modulates them. These velocity-modulated electrons pass through the field-free drift space defined by drift tube I85 and become at least partially bunched b the time they arrive at the gap between grids I98 and I92 of resonator I81. Resonator I81,

which may be termed a floating resonator,

since ordinarily it is not connected to any load or other source, is tuned to the harmonic of the input fundamental frequency whioh it is desired to produce. The partially bunched electron stream contains a current component of the fundamental frequency and also components of many harmonics of the fundamental frequency, including the desired harmonic to which resonator I81 is tuned.

In this way the electron stream excites resonator I81'to oscillate at 'thisdes'ire'd "harmonic frequency, thereby producing an axial alternating electric field component of this harmonic frequency between grids I90 and I 92. This harmonic electric field further velocity-modulates the electrons of the stream so that after their subsequent passage through the further drift space defined by drift tube I85, the desired harmonic frequency energy content of the electron stream is enriched by the time these electrons arrive at the corresponding grids of resonator I95. In this way greatly increased amounts of harmonic frequency energy are supplied to resonator I95 by the electron stream and are available to be supplied to any load coupled to the concentric transmission line terminals I91.

In effect, resonators I83 and I8I coupled by drift tube I85 form a driven frequency multiplier, while resonators I81 and I95 coupled by drift tube I85 form a harmonic frequency amplifier. Since these multiplying and amplifying stages utilize the same electron stream, no additional power is needed for amplification over that required for frequency multiplication, so that for the same amount of input beam power and input fundamental frequency power, greatly increased amounts of high frequency energy can be derived from the output resonator I95 ovcr equivalent prior art systems. In this way we have provided for a much simpler and much more highly efficient device for producing frequency multiplication at super-high frequencies.

It is to be noted that such a system, in addition to the advantage (over the prior art system of Patent No. 2,281,935) of reducing the number of harmonic frequency resonant circuits to be tuned and maintained in alignment, has the fur-. ther advantage with respect to a separate multiplier and amplifier system such as shown in the above-mentioned patent, in that the last resonator of the multiplier of this patent being coupled to the first resonator of the amplifier and being loaded thereby, necessarily has a lower effective shunt impedance than is the case of the floating resonator I8! or the output resonator I95 of the present invention. This increased shunt impedance of the resonators of the pres ent invention causes a much improved amplifying action further tending to increase the output and efficiency.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. Frequency-multiplying and amplifying apparatus comprising means for producing an electron stream, a first cavity resonator having a pair of electron-permeable grids forming portions of the walls thereof and positioned in alignment with the path of said stream, said first resonator being tuned substantially to the fundamental frequency to be multiplied, a drift tube surrounding said stream path beyond said grids. a second cavity resonator having a pair of electron-permeable grids forming portions of the walls thereof and positioned in alignment with the path of said stream beyond said drift tube, said second cavity resonator being floating and tuned substantially to a desired harmonic of said fundamental frequency, a second drift tube surrounding said stream path beyond said second resonator, and an output cavity resonator having a pair of electron-permeable grids forming portions of the walls thereof and positioned in alignment with said stream path beyond said second drift tube, said output resonator being also tuned substantally to said harmonic frequency.

2. Frequency-multiplying apparatus comprising means for producing an electron stream, a first cavity resonator along the path of said stream and tuned substantially to a fundamental frequency to be multiplied, a second floating cavity resonator positioned along said stream path spaced from said first resonator and tuned substantially to a harmonic of said fundamental frequency, and a third cavity resonator along said stream path beyond said second resonator -and also tuned substantially to said harmonic frequency.

3. A frequency multiplier electron discharge tube comprising a source of electrons, means for forming said electrons into a stream, means positioned in alignment with the path of said stream consisting of a single apparatus tuned to a predetermined frequency for causing said electrons to form recurrent bunches, means positioned in alignment along the path of said stream comprising a cavity resonator tuned to a harmonic of said frequency for extracting energy from said bunched electrons, and a further cavity resonator means tuned to said harmonic frequency and coupled to said stream for further extracting energy from said stream.

4. Frequency-multiplying apparatus comprising means for producing an electron stream, three pairs of closely spaced electron-permeable grids positioned in spaced relation in alignment with the path of said stream, a fundamental frequency tuned circuit coupled to one of said pairs and having an input terminal coupled thereto, a pair of harmonic frequency tuned circuits coupled respectively to the others of said grid pairs, and an output terminal coupled to one of said harmonic frequency circuits.

5. Apparatus as in claim 4 wherein the other of said harmonic frequency circuits is floating.

6. Apparatus as in claim 4 including a further output terminal coupled to the other of said harmonic frequency circuits.

' WILLIAM W. HANSEN.

JOHN R. WOODYARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,222,899 Fraenckel Nov. 26, 1940 2,281,935 Hansen May 5, 1942 2,305,883 Litton Dec. 22, 1942 2,392,379 Hansen Jan. 8, 1946 2,394,396 Mouromtseff et al. Feb. 5, 1946 2,396,802 Mouromtseff et a1. Mar. 19, 1946 2,425,738 Hansen Aug. 19, 1947 

